Ad hoc networks are constructed autonomously and instantly in response to communications between a plurality of radio devices. In ad hoc networks, when two interacting radio devices are not located in the same communication area, a radio device that is located between the two radio devices functions as a router and relays data packets. In this way, large multi-hop networks are formed.
Dynamic routing protocols that support multi-hop communications are classified into two categories: table-driven protocols and on-demand protocols. Table-driven protocols periodically exchange route control information and preestablish the routing table. Known table-driven protocols include FSR (Fish-eye State Routing), OLSR (Optimized Link State Routing) and TBRPF (Topology Dissemination Based on Reverse-Path Forwarding).
On-demand protocols establish routes to the destination only when data transmission is required. Known on-demand protocols include DSR (Dynamic Source Routing) and AODV (Ad Hoc On-Demand Distance Vector Routing).
In conventional ad hoc networks, when data is transmitted from source to destination, the communication route is determined so that the number of hops from source to destination is as small as possible (Guangyu Pei, et al., “Fisheye state routing: a routing scheme for ad hoc wireless networks,” ICC2000. Commun., Volume 1, L.A., June 2000, pp. 70-74.)
However, as the wireless environment is unstable, the route with small hop numbers does not necessarily guarantee the quality. Therefore, it is better to select only stable routes in some way. Known major methods thereof are methods of introducing signal strength thresholds and methods of measuring packet loss rates.
The methods of measuring packet loss rates work effectively when packet loss is happening continuously.
The methods of introducing signal strength thresholds include a known method of extracting stable routes based on the average signal strength.
Non-patent Document 1: Rohit Dube, Cynthia D. Rais, Kuang-Yeh Wang, and Satish K. Tripathi, “Signal Stability-based Adaptive Routing (SSA) for Ad Hoc Mobile Networks,” IEEE Personal Communications, February 1997, pp. 36-45.)